I was just reading a few articles on this site that recommended using 2 filters. I currently have a HOB filter that came with my kit. Ive read conflicting reviews regarding it's efficiency. My tank is only a few weeks old so I cannot make any claims but was wondering if I should invest in another filter? If so, would I want another HOB filter? I read it's best to buy a filter advertized for a tank twice the size you have, if this is so, would I want the second filter to be meant for a tank twice the size I have, the same size of tank, or smaller?